Tissues — Science STD 9 — Question

Which of the following are physical changes and which are chemical changes?

1. Burning of a magnesium wire.
2. Freezing of water.
3. Rusting of iron.
4. Glowing of an electric bulb.

Write the formula for work done on a body when the body moves at an angle to the direction of force. Give the meaning of each symbol used.

An object is moving along a straight line with uniform acceleration. The following table gives the velocity of the object at various instants of time:

Time (in sec.):	0	1	2	3	4	5	6
Velocity (in m/s):	2	4	6	8	10	12	14

Plot the graph. From the graph,

1. Find the velocity of the object at the end of 2.5 seconds.
2. Calculate the acceleration.
3. Calculate the distance covered in the last 4 seconds.

A boy throws a rubber ball vertically upwards. What type of work, positive or negative, is done:

1. By the force applied by the boy?
2. By the gravitational force of earth?

What would you observe when: A saturated solution of potassium chloride prepared at 60°C is allowed to cool to room temperature.

Explain the meaning of the following equation of motion:
v = u + at
where symbols have their usual meanings.

What is the fraction of the mass of water due to neutrons?

Give an example of a average daily feed of a cow.